1. Field of the Invention
The invention relates to a group communication method and a device, a method for forming of a group of terminal devices.
2. Description of the Related Art
Electronic devices become smaller, lower in power requirements, and less expensive, the bodies are adorned with personal information and communication appliances. Such devices include cellular phones, personal digital assistants (PDAs), pocket video games, and pagers. The concept of Personal Area Networks (PANs) is known to illustrate how electronic devices on and near the human body can exchange digital information by capacitively coupling small currents through the body. A low-frequency carrier is used. A prototype PAN system allows users to exchange electronic business cards by shaking hands.
PAN devices are used in worn objects. They are watches, credit cards, eyeglasses, identification badges, belts, waist packs, and shoe insert. Head-mounted PAN devices include headphones, hearing aids, microphones, and head-mounted displays. Shirt pocket PAN devices operate as identification badges. The wristwatch operates as a location for a display, a microphone, a camera, and a speaker. PAN devices incorporating sensors provide medical monitoring for bodily functions (heartbeat, blood pressure, and respiratory rate). Wallet-based PAN devices store information and identify the possessor. Shoe inserts are self-powered and provide a data-link to remote PAN devices located in the workstations and floor transponders that detect the location and identity of people.
Advances in telecommunication systems technology have resulted in a variety of systems and services being available for system users. These systems include cellular telephone systems providing mobile telephone services. The cellular telephone systems provide services that allow subscribers of these systems to increase their accessibility and be reachable, potentially at all times, and as long as the subscribers remain in the service areas covered by their systems.
In a cellular system, a person desiring to contact the cellular subscriber would simply dial the phone number of the cellular subscriber to contact the subscriber at the subscriber's cellular telephone. As long as the cellular subscriber kept the cellular telephone powered on the subscriber would be accessible when located within the coverage area of the cellular system.
Normally the system sets up a call between the cellular telephone or a so-called mobile terminal and another mobile terminal or a subscriber of a public switched telephone network PSTN. Dialing the subscriber number of the mobile terminal or the like sets up a call to the given mobile terminal. In group calls the whole group is called with a single dialed number, i.e. a group number. A group call is a conference call in which all participants may talk in turn and hear one another. An individual mobile radio may belong to a plurality of groups programmed into the mobile radio. The system keeps a file on the base stations associated with the group number of each group. A group call may cover one, several or all base stations within the area of a mobile exchange or a plurality of mobile exchanges.
Some mobile networks include short message services, e.g. SMS is a bi-directional service in GSM for short alphanumeric messages or data in similar form. In SMS it is possible to deliver a message to the mobile terminal even during an established call, and to deliver a message using so-called store-and-forward service, in which the message is stored in the network, if the mobile terminal is unavailable, and forwarded shortly after the mobile terminal can be reached again. In the traditional GSM system data services are based on circuit switched technology providing maximum data transfer rate of 9,6 kbit/s for transparent and non-transparent bearer services for data communication. Along with an increasing data volume, demand for higher transfer rates has arisen so that the GSM system has been developed to include as an extension the so-called General Packet Radio Service (GPRS) as a packet switched data service.